<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 400px;
            height: 300px;
            display: flex;
            border: 1px solid #000;
            /* justify-content: start; */
            /* justify-content: end; */
            /* justify-content: space-between; */
            /* justify-content: space-around; */
            /* justify-content: space-evenly; */
            /* justify-content: stretch; */
            /* align-items: start end space-between space-around space-evenly stretch; */
        }
        .inner{
            width: 100px;
            height: 100px;
            border: 1px solid #000;
            text-align: center;
        }
        .inner:nth-child(1){
            /* align-self: flex-end; */
            flex: 1;
        }
        .inner:nth-child(2){
            flex: 3;
        }
        .inner:nth-child(3){
            flex: 2;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="inner">1</div>
        <div class="inner">2</div>
        <div class="inner">3</div>
    </div>
</body>
</html>